I'd use the blaster on both the dash and the rest of the cab, and would take the time to take it all apart as Heavy said...
I totally disassembled mine, sandblasted it really good repainted and it looks super...
You can try to cut corners by hand sanding or masking things without removing them, but often won't get as good of a result or may damage something and have to replace it if you don't do it right the first time so that's the direction I'd go...
Just my $0.02...
~Trev
